Lens barrel

ABSTRACT

This lens barrel comprises a first group frame supported by two first guide shafts and a second guide shaft such that it is capable of being advanced or retracted, a focus frame, a focus frame holding portion, and a third group frame. The first guide shafts are bonded and supported by the focus holding frame in parallel such that both ends thereof are exposed. The first group frame and the third group frame are supported slidably by both end portions. Further, the second guide shaft supports the focus frame slidably. An end of the second guide shaft is supported through a short fitting length while it is not fixed to the first group frame and the other end thereof is supported slidably by the third group frame through a short fitting length. Therefore, in this lens barrel, the accuracy in advancement and retraction of respective members is excellent and an efficiency of storage space is excellent thereby contributing to reduction of the size, achieving compactness.

[0001] This application claims benefit of Japanese Applications No. Hei11-368191 filed in Japan on Dec. 24, 1999 and No. Hei11-368194 filed in Japan on Dec. 24, 1999, the contents of which are incorporated by this reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the invention

[0003] The present invention relates to a frame member supporting structure of a lens barrel having plural movable frame members.

[0004] 2. Related Art Statement

[0005] In recent years, compact cameras have been reduced in size and employed high-magnification zoom function and other novel function. Corresponding to these trends, various types of moving frames retracting mechanisms of the lens barrel have been proposed.

[0006] For example, in a lens barrel employing the moving frame positioning method disclosed in Japanese Patent Application Laid-Open No. HEI4-52629, a bar-like guide member for supporting a third moving frame slidably with respect to first and second moving frames is employed. The bar-like guide member is fixed to the first or second moving frame such that an end or both ends of the bar-like guide member are held by the first or second moving frame and the third moving frame is supported slidably by the guide member.

[0007] Because in the aforementioned lens barrel, an end of the bar-like guide member or both ends thereof are fixed to a movable frame, a space around that fixing portion becomes a waste space. At the same time, this is an obstacle for a disposition space for other structural members. In case of cantilever structure in which an end of the bar-like guide member is supported, the span of the bar-like guide member is long, so that the defection thereof is increased. Therefore, it is difficult to make a thin bar-like guide member, which is an obstacle against reduction of the size of the lens barrel.

[0008] In the lens barrel disclosed in the aforementioned Japanese Patent Application Laid-Open No. HEI4-52629, a fourth moving frame is supported such that it is capable of being advanced or retracted relative to the third moving frame. Thus, other two bar-like guide members are provided additionally. As a result, to hold four moving frames such that they are capable of being advanced or retracted, four bar-like guide members are disposed. These guide members are fixed completely to any of the moving frames. Thus, a very highly accurate configuration and dimension are demanded for the moving frame and the guide members, thereby leading to increase of part cost. Further, because the quantity of the guide members is large, there is also such a problem that it takes long for assembly work.

SUMMARY OF THE INVENTION

[0009] The present invention has been achieved to solve the above-described problems and an object of the invention is to provide a lens barrel having an effect of reducing part cost, easy to assemble, having an excellent space efficiency and enabling reduction of the size and compactness.

[0010] The lens barrel according to an aspect of the present invention comprises a first frame, a second frame, a third frame, and a first supporting member both ends of which are fixed to the second frame such that they are exposed. The first and third frames are supported by the first supporting member.

[0011] Further, a lens barrel according to another aspect of the present invention has a first frame, a second frame, a third frame, a fourth frame, a first supporting member both ends of which are fixed to the second frame such that they are exposed and a second supporting member which is supported by the first frame and third frame. The first frame and the third frame are supported by the first supporting member and the fourth frame is supported by the second supporting member.

[0012] Other features and benefits of the present invention will be apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is an exploded view of a lens barrel according to an embodiment of the present invention;

[0014]FIG. 2 is a perspective view showing a state in which a guide shaft and a focus holding frame are supported by a first assembly jig for guide shaft positioning in a lens barrel of the aforementioned embodiment;

[0015]FIG. 3 is a perspective view of a second assembly jig for lens/frame member positioning to be applied to the lens barrel assembly of the embodiment;

[0016]FIG. 4 is a perspective view of a third assembly jig for lens/frame member positioning to be applied to the lens barrel assembly of the embodiment;

[0017]FIG. 5 is a longitudinal sectional view showing an assembly condition of the lens barrel using the second and third assembly jigs in the lens barrel of the embodiment;

[0018]FIG. 6A is an enlarged sectional view showing a section of a bonding portion between the lens group and frame member in the lens barrel of the embodiment such that the frame member is protruded relative to the lens group;

[0019]FIG. 6B is an enlarged sectional view showing a section of a bonding portion between the lens group and frame member in the lens barrel of the embodiment such that the lens group is protruded relative to the frame member;

[0020]FIG. 6C is an enlarged sectional view showing a section of a bonding portion between the lens group and frame member in the lens barrel of the embodiment such that the frame member and the lens group are located on substantially the same surface;

[0021]FIG. 7 is a longitudinal sectional view after the lens barrel of the embodiment is assembled;

[0022]FIG. 8 is a sectional view (partial sectional view) taken along the line I-I of FIG. 7; and

[0023]FIG. 9 is a development view of a cam groove in cam ring applied to the lens barrel of the embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0025]FIG. 1 is an exploded view of a lens barrel of a preferred embodiment. FIG. 2 is a perspective view showing a state in which a guide shaft and a focus holding frame are supported by a first assembly jig for guide shaft positioning in a lens barrel of the aforementioned embodiment. FIG. 3 is a perspective view of a second assembly jig for lens/frame member positioning of the lens barrel. FIG. 4 is a perspective view of a third assembly jig for lens/frame member positioning of the lens barrel. FIG. 5 is a longitudinal sectional view showing an assembly condition of the lens barrel using the second and third assembly jigs for lens/frame positioning. FIGS. 6A, 6B, 6C are enlarged sectional views showing a shape of a bonding portion between the lens group and lens holding frame in the lens barrel. FIG. 6A shows a case where the lens holding frame is protruded relative to the lens. FIG. 6B shows a case where the lens group is protruded relative to the lens holding frame. FIG. 6C shows a case where the lens holding frame and the lens are located on substantially the same surface. FIG. 7 is a longitudinal sectional view after the lens barrel of the embodiment is assembled. FIG. 8 is a sectional view taken along the line I-I of FIG. 7, indicating a partial section of a portion around the guide shaft in the lens barrel. FIG. 9 is a development view of a cam groove in cam ring applied to the lens barrel of the embodiment.

[0026] In the above description, it is assumed that an object side of the lens barrel is forward and an image side is backward. A rotation direction of a cam ring or the like is indicated when viewed from forward (object side).

[0027] The lens barrel 1 of this embodiment is incorporated in a zoom camera or used as an interchangeable type zoom lens barrel. As shown in FIG. 1 and the like, the lens barrel 1 comprises a float key 3 (see FIG. 7) whose rotation is restricted and which is supported so as to be capable of being advanced or retracted, a cam ring 2 which is capable of being advanced and retracted together with the float key 3 and which is supported rotatably, a first group frame 4, which is a first frame (moving frame member) advanced or retracted relatively by the cam ring 2, a first group lens (optical element) 21 held by the first group frame 4, a focus holding frame 6, which is a second frame (moving frame member) advanced or retracted relatively by the cam ring 2, a focus frame 5, which is a fourth frame (moving frame member) advanced or retracted by a focus driving mechanism (not shown) relative to the focus holding frame 6, second group lens (optical element) comprised of second group lens (front) 22, second group lens (middle) 23 and second group lens (rear) 24, which are focus lenses held by the focus frame 5, and a shutter 15 incorporated in the focus frame 5. Further, the lens barrel 1 comprises a third group frame 7, which is a third frame member (moving frame) advanced or retracted relatively by the cam ring 2, a third group lens (front) 25 and third group lens (rear) 26 composing the third lens (optical element) held by the third group 7, guide shafts 8, 9, which are first guide members (first supporting members) for attached the focus holding frame 6 and supporting the first frame 4 and the third frame 7 slidably and a guide shaft 11, which is a second guide member (second supporting member) supported by the first group frame 4 and third group frame 7 and for supporting the focus frame 5 slidably through a sleeve 10.

[0028] As shown in the development diagram of FIG. 9, the cam ring 2 has three pairs of cam portions in which a length direction of a groove thereof is comprised of three rows along the rotation direction as shown in a development diagram of FIG. 9.

[0029] Each pair of the aforementioned cam portion is comprised of a cam groove 2 a in which a cam follower (will be described later) 4 i is fit slidably, a cam groove 2 b in which a cam follower (will be described later) 6 i is fit slidably, a cam groove 2 c in which a cam follower (will be described later) 7 i is fit slidably, a cam follower introducing groove 2 d, which is an introducing portion for insertion of the aforementioned cam followers 4 i, 6 i, 7 i for assembly and a joint groove 2 e, which is a joint portion for insertion of the cam follower 4 i for assembly.

[0030] The cam follower introducing groove 2 d is an introducing groove leading from an opening portion 2 g in an end face 2 f on image side of the cam ring 2 to ends of the cam grooves 2 a, 2 c. The introducing groove 2 d is formed at an introducing position θA outside a tele end position θT of a rotation position of the cam ring 2, which will be described later, such that it is parallel to an optical axis O.

[0031] The joint groove 2 e is a joint portion connected to an end of the cam groove 2 a to an end of the cam groove 2 b. The joint groove 2 e is formed at a switch position θB outside a collapsed position θC of a rotation position of the cam ring 2, which will be described later, such that it is parallel to the optical axis O.

[0032] The cam groove 2 c is provided on the image side of the cam ring 2 in a range from the introducing position θA to the switch position θB and includes a collapsed range cam groove 2C1 existing inside that range between the collapsed position θC and a wide end position θW and a zoom range cam groove 2C2 existing between a wide end position θW and a tele end position θT.

[0033] The aforementioned cam grooves 2 a, 2 b are joined through the joint groove 2 e and are formed to extend side by side in a range from the introducing position θA of the rotation position of the cam ring 2 to the switch position θB. Then, the cam grooves 2 a, 2 b have collapsed range cam grooves 2 a 1, 2 b 1 existing between the collapsed position θC and the wide end position θW inside the aforementioned range and zoom range cam grooves 2 a 2, 2 b 2 existing between the wide end position θW and tele end position θT.

[0034] Therefore, in a cam portion provided in the cam ring 2, the opening portion 2 g on the end face 2 f of the image side leads to the cam follower introducing groove 2 d. The introducing groove 2 d leads to the cam grooves 2 c and 2 b. The cam groove 2 b leads to the joint groove 2 e. The joint groove 2 e lead to the cam groove 2 a.

[0035] The cam grooves 2 a, 2 b form a pair of continuous cam grooves connected through the joint groove 2 e. Three pairs of the continuous cam grooves are provided in the cam ring 2. The aforementioned three pairs of the continuous cam grooves 2 a, 2 b are disposed in an inner circumferential face of the cam ring 2 such that they overlap each other in the rotation direction in a condition that they do not cross each other but invade each other.

[0036] The cam ring 2 incorporated in the lens barrel 1 is extended from the collapsed position in the direction of the optical axis O along the float keys 3 by an extension driving mechanism (not shown) to a photographing position. Further, the cam ring 2 is rotated from the collapsed position θc to the wide end position θw by a zoom driving mechanism (not shown).

[0037] Upon zooming operation, the cam ring 2 is rotated in an interval from the wide end position θw to the tele end position θt (see FIG. 9). Accompanied by the rotation, the cam follower is driven through each cam groove so that respective members of the first group frame 4 are advanced or retracted. The position of the cam ring 2 indicated by the rotation position (rotation angle) θ is indicated by a relative rotation position of the aforementioned cam followers 2 a, 2 b, 2 c with respect to the cam follower rows (fixed).

[0038] The first group frame 4 includes an outer peripheral portion 4 j, a backward protruded lens holding portion 4 a, which is protruded along the optical axis and has a pawl portion 4 g, backward protruded boss portions 4 b, 4 c disposed at two positions up and down in the frame portion and extended along the optical axis, a shaft hole 4 f in which a front end of a guide shaft 11 is to be fit, and three cam followers 4 i attached to the outer peripheral portion and capable of entering the cam groove 2 a.

[0039] An inner circumference of the protruded lens holding portion 4 a has a tolerance securing a gap for loose fitting with respect to an outer circumference of the first group lens 21 to be mounted. This gap is of an appropriate dimension absorbing disparity of the dimensions of relating frames and lens member and a dimension allowing adhesive agent to be filled with. Additionally, there is a gap in the optical axis O direction between the position of the pawl portion 4 g and the face of the first group lens 21. That gap absorbs the disparity of the dimension of the relating frames of the optical axis O and lens members and a dimension allowing adhesive agent to be filled with.

[0040] The boss portion 4 b has the shaft hole 4 d which the guide shaft 8 is capable of being fit slidably when it is precision fit. On the other hand, the boss portion 4 c has an long hole 4 e in which the guide shaft 9 is capable of being fit slidably when it is precision fit around the optical axis O. The aforementioned shaft hole 4 f is a hole having a relatively small depth in which the guide shaft 11 is fit when it is precision fit.

[0041] Meanwhile, the precision fitting condition refers to a state in which there is no looseness between the hole portion and shaft portion or a state in which the fitting is attained with extremely little looseness. Fitting with loose, which will be described later, refers to a state in which the fitting is attained with a gap. Further, fitting slidably, which will be described later, refers to a fitting condition with a slight gap.

[0042] The focus holding frame 6 has shaft holes 6 a, 6 b disposed up and down in the frame portion and in which the guide shafts 8, 9 are fit with loose, an escape hole 6 c disposed sideways of the shaft hole 6 a and which the guide shaft 11 passes through, three cam followers 6 i capable of being fit into the cam groove 2 b, and a fitting inner circumferential portion 6 e. Further, the focus holding frame 6 contains a focus driving portion such as a feeding screw mechanism for focus-driving the focus frame 5, which will be described later, (not shown).

[0043] The guide shafts 8, 9 are bonded into the shaft holes 6 a, 6 b with the assembly jig 31 for guide shaft positioning, which will be described later, in a positioning condition. The escape hole 6 c is an escape hole in which a sleeve 10 is capable of entering with the guide shaft 11. The fitting inner circumferential portion 6 e is capable of being fit to the fitting outer circumferential portion 5 f of the focus frame 5, which will be described, in a sliding condition.

[0044] The focus frame 5 includes lens holding portions 5 d and jig escaping portions 5 g, provided by dividing a front inner circumferential portion to three parts, shutter incorporating concave portion 5 i and lens holding portion 5 j provided in the inner circumferential portion in the center, three protruded lens holding portions 5 e extended in the optical axis direction provided in the rear and an outer circumferential portion 5 f to be fit to the focus holding portion 6 provided on an outer circumference in the rear. Further, the focus frame 5 includes an escape portion 5 h for the guide shaft 8 disposed in an upper portion of the frame, a sleeve fitting hole 5 a disposed sideways of the escape portion 5 h and U-shaped groove 5 c disposed in a lower portion of the frame and capable of being fit to and making a sliding contact with the boss portion 4 c of the first group frame 4 when it is precision fit.

[0045] The inner circumferences of the lens holding portion 5 d jig and lens holding portion 5 e have a tolerance of dimension containing a gap with respect to the outer diameters of the second group lens (front) 22 and second group lens (rear) 24 to be mounted, thereby absorbing disparity of dimension of relating frames and lens members and providing a sufficient gap allowing adhesive agent to be filled with.

[0046] A lens contacting face 5 k which makes a contact with a lens face of the second group lens (front) 22 to be mounted is provided in the rear in the direction of the optical axis O of the lens holding portion 5 d. Further, a lens contacting face 5 m, which makes contact with a lens face of the second group lens (rear) 24, is provided forward in the direction of the optical axis O of the lens holding portion 5 e.

[0047] The lens holding portion 5 j has an inner periphery which an outer circumference of the second group lens (middle) 23 is precision fit to and the second group lens (middle) 23 is directly bonded thereto.

[0048] The diameter of the sleeve fitting hole 5 a is as large as the sleeve 10 can be fit thereto with loose, thereby absorbing disparity of dimension of the relating frames and lens members and providing a dimension allowing adhesive agent to be filled with.

[0049] The third group frame 7 includes a front end face portion 7 h, an outer peripheral portion 7 g, lens holding portions 7 d and jig escaping portions 7 e divided to three sections by the front end face portion 7 h, a shaft hole 7 a disposed in a upper portion and in which the guide shaft 8 is fit slidably in precision fitting condition, a long hole 7 b disposed in a lower portion of the frame and which the guide shaft 9 is fit slidably in the direction of the optical axis O around the optical axis O in precision fitting condition, and a shaft hole 7 c relatively short disposed sideways of the shaft hole 7 a and which the guide shaft 11 is precision fit.

[0050] Further, the third group frame 7 includes three cam followers 7 i attached to the outer peripheral portion 7 g and capable of being fit to the cam groove 2 c and three advancement guide protrusions 7 f disposed on a rear flange of the outer peripheral portion 7 g.

[0051] Here, the reason why the aforementioned shaft hole 4 f and the shaft hole 7 c are relatively short fitting holes will be described. While these two shaft holes 4 f and 7 c are fit to the guide shaft 11, the guide shaft 11 is capable of being tilted slightly because such a relatively short fitting length is provided. How much the guide shaft 11 is capable of being tilted depends upon a minimum distance between the first group frame 4 and the third group frame 7 and positional accuracies of the shaft holes 4 f, 7 c with respect to the guide shaft holes 4 d, 7 a in the first group frame 4 and third group frame 7. That is, it is largely relating to an error of a relative distance between the guide shaft hole 4 d and the shaft hole 4 f and an error of a relative distance between the guide shaft hole 7 a and the shaft hole 7 c. The guide shaft 11 needs to be tilted more as these two errors are absorbed. Naturally, if these errors are small, the fitting accuracy between the guide shaft 11 and the shaft holes 4 f, 7 c is intensified, so that if the fitting length is increased, the tiltable angle of the guide shaft 11 may be small. However, if these errors are large, the fitting accuracy must be lowered while the fitting length must be shortened. In this case, the assembly accuracy of the lens barrel drops.

[0052] In other words, the tiltable angle of the guide shaft is determined by the aforementioned minimum distance and two errors. Then, the fitting accuracy between the hole and guide shaft and the fitting length are determined. Generally, that angle should be determined by the fitting length without lowering the fitting accuracy. That is, the guide shaft 11 can be tilted by decreasing the fitting length.

[0053] An inner circumference of the lens holding portion 7 d has a tolerance of dimension having a gap with respect to the outer diameter of a fitting portion of the third group lens (front) 25 to be mounted, thereby absorbing disparity of dimension of the relating frames and the lens member and providing a dimension allowing adhesive agent to be filled with.

[0054] There is a gap in the direction of the optical axis between an inner end face 7 k of the lens holding portion 7 d and a flange face 25 a of the third group lens (front) 25. That gap absorbs disparity of dimension of the relating frames and lens members and provides a sufficient gap allowing adhesive agent to be filled with.

[0055] When assembling the lens barrel 1 of this embodiment having such a structure, the first assembly jig 31 for guide shaft positioning shown in FIG. 2, the second assembly jig 32 for lens/holding frame positioning shown in FIGS. 3, 4 and the third assembly jig 33 are used.

[0056] As shown in FIG. 2, the first assembly jig 31 for guide shaft positioning has V-grooves 31 a, 31 b disposed up and down in an outer periphery for holding the guide shafts 8, 9 at a predetermined separating distance in parallel to the optical axis O and an outer circumferential portion 31 c for positioning capable of being precision fit to the fitting inner circumferential portion 6 e of the focus holding frame 6.

[0057] The second assembly jig 32 for lens/holding frame positioning is a cylinder partitioned to front and rear by a wall portion (a backward wall face 32 g is assumed to be 32 g) as shown in FIG. 3 and has a forward inner peripheral face 32 a and a backward inner peripheral face 32 b. The forward inner peripheral face 32 a has a stopper 32 j for positioning the focus holding frame 6 in the direction of the optical axis O.

[0058] A front face of the wall portion has three protruded lens supporting portions (inner peripheral face) 32 e which are protruded in the direction of the optical axis and a lens contact face 32 f which is disposed in the rear of the supporting portions. Further, a rear face thereof has three protruded lens supporting portions (inner peripheral face) 32 h, which are protruded in the direction of the optical axis and a lens contact face 32 i, which is disposed in front of the inner peripheral portion. Further, the aforementioned wall portion has escaping holes 32 c, 32 d.

[0059] The forward inner peripheral face 32 a is an inner peripheral face which the outer peripheral portion 4 j of the first group frame 4 and the outer peripheral face 33 a of the assembly jig 33 are capable of being precision fit. The backward inner peripheral face 32 b is an inner peripheral face which the outer peripheral portion 7 g of the third group frame 7 is capable of being precision fit.

[0060] The lens supporting portions (inner peripheral face) 32 e, 32 h are inner peripheral faces which the outer peripheries of the second group lens (rear) 24, third group lens (front) 25 are capable of being precision fit.

[0061] As shown in FIG. 4, the second assembly jig 33 for the lens/holding frame positioning is a substantially circular jig having an outer peripheral face 33 a. Three divided protruded lens supporting portions 33 b are provided such that they are protruded in the direction of the optical axis and lens contact faces 33 c are provided in the rear of each inner peripheral portion. A rear face of the second assembly jig 33 has three divided protruded lens supporting portions (inner peripheral faces) 33 d, which are protruded in the direction of the optical axis, lens contact faces 33 e provided in the rear of each inner peripheral portion and escaping portions 33 f provided up and down in the outer frame.

[0062] Inner peripheral faces of the lens supporting portions 33 b, 33 d are inner peripheral faces which the outer peripheries of the first group lens 21 and second group lens (front) are capable of being precision fit.

[0063] To attach the guide shafts 8, 9 to the focus holding frame 6 when assembling the lens barrel 1, as shown in FIG. 2, using the first assembly jig 31, the outer circumferential portion 31 c for frame positioning is fit to the fitting inner circumferential portion 6 e of the focus holding frame 6.

[0064] Then, the guide shafts 8, 9 inserted through the shaft holes 6 a, 6 b in the focus holding frame 6 are fixed in the V-grooves 31 a, 31 b of the assembly jig 31. Because the shaft holes 6 a, 6 b have a gap with respect to the guide shafts 8, 9, the guide shafts 8, 9 are kept at a predetermined position in the direction of the optical axis with a predetermined distance between the shafts such that they are parallel to the optical axis.

[0065] With the above supporting condition, adhesive agent (fixing agent) is poured through adhesive agent pouring holes 6 f, 6 g in the focus holding frame 6 so as to fix the guide shafts 8, 9 in the shaft holes 6 a, 6 b.

[0066] Next, the assembly jigs 32, 33 are employed in order to assemble respective lens barrel components around the focus holding frame 6 having the guide shafts 8, 9. Meanwhile, upon assembly, the assembly jig 32 shown in FIG. 3 is inserted between insertion positions b1 and b2 with respect to the lens barrel 1 shown in FIG. 1. Then, the assembly jig 33 shown in FIG. 4 is inserted between insertion positions a1 and a2 with respect to the lens barrel 1 shown in FIG. 1.

[0067] In the assembly jig 32 shown in the longitudinal sectional view of FIG. 5, the outer peripheral face of the second group lens (rear) 24 is fit to the inner peripheral face of the lens supporting portion 32 e such that the second group lens face is in contact with the lens contact face 32 f.

[0068] On the other hand, the outer peripheral face of the second group lens (front) 22 is fit to the inner peripheral face of the lens supporting portion 33 d of the assembly jig 33 such that the aforementioned lens face is brought into contact with the lens contact face 33 e.

[0069] Then, the focus holding frame 6 having the guide shafts is inserted up to a reference position where it comes into contact with a stopper 32 j of the assembly jig 32, on which the lens is mounted, from forward in the direction of the optical axis.

[0070] Further, the fitting outer circumferential portion 5 f of the focus frame 5, to which the second group lens (middle) 23 is bonded, is fit to the fitting inner circumferential portion 6 e of the focus holding frame 6 and inserted until the lens contact face 5 m of the focus frame 5 comes into contact with the front lens of the second group lens (rear) 24. At this time, the aforementioned stopper of the jig is set such that the focus holding frame 6 is floated with a gap with respect to the stopper in the direction of the optical axis.

[0071] Then, the guide shafts 8, 9 are inserted into the escaping portion 5 h and U-groove 5 c in the focus frame 5. Further, the sleeve 10 is inserted into the sleeve fitting hole 5 a in the focus frame 5 and inserted into the escaping hole 6 c in the focus holding frame 6.

[0072] After that,, the aforementioned assembly jig 33, on which the lens is mounted, is fit to the forward inner peripheral face 32 a of the assembly jig 32 and the rear lens face of the second group lens (front) 22 is inserted until it comes into contact with the lens contact face 5 k of the focus frame 5. At this time, the protrusion of the lens supporting portion 33 d of the assembly jig 33 is fit into the escaping portion 5 g of the focus frame 5.

[0073] Then, the first group frame 4 is installed. Before the installation, the guide shaft 11 is inserted into the shaft hole 4 f in the first group frame 4 and an E-ring 12 is embedded into an E-ring groove 11 a in a front end of the guide shaft (See FIG. 8). The guide shaft 11 is capable of being advanced or retracted with the first group frame 4 by this E-ring 12.

[0074] The first group frame 4 with the guide shaft 11 is inserted up to a reference position in the direction of the optical axis in front of the assembly jig 33, where it comes into contact with a stopper (not shown) of the assembly jig 32 or an end of the pawl portion 4 g of the first group frame 4 comes into contact with the escaping portion 33 g in the jig 33. At this time, the guide shaft 8 is fit into the shaft hole 4 d in the first group frame 4 and the guide shaft 9 is fit into the long hole 4 e in the first group frame 4.

[0075] Further, the boss portion 4 c of the first group frame 4 is fit into the U-groove 5 c of the focus frame 5. After fitting the sleeve 10 on the focus frame 5, the guide shaft 11 is held such that it is passed through the escaping hole 6 c in the focus holding frame 6.

[0076] After that, if the first group lens 21 is inserted into the first group frame 4, the first group lens 21 comes into contact with the lens contact face 33 c of the jig 33 such that it is floated with respect to the first group frame 4. Consequently, the outer circumference of the first group lens 21 is precision fit to the lens supporting portion 33 b and supported by the jig 33.

[0077] Subsequently, the third group frame 7 is fit loosely to the backward inner peripheral face 32 b of the assembly jig 32 and then inserted up to a reference position in the direction of the optical axis where an end face portion 7 h thereof comes into contact with the wall portion 32 g. At that time, the guide shafts 8, 9, 11 are fit into the shaft hole 7 a, long hole 7 b and shaft hole 7 c. The protrusion of the lens supporting portion 32 h of the jig 32 is fit into the escaping portion 7 e of the third group frame 7.

[0078] With the third group frame 7 inserted, the third group lens (front) 25 is fit into the inner peripheral portion of the lens supporting portion 32 h of the assembly jig 32 and a lens end face thereof is brought into contact with the lens contact face 32 i for positioning.

[0079] With the respective lens barrel components set in the aforementioned assembly jigs 32, 33, the first group frame 4 and the third group frame 7 are positioned at the optical axis O position at a predetermined precision in the direction of the optical axis O through the respective fitting shaft holes by the guide shafts 8, 9 supported by the focus holding frame 6 (see FIG. 7). Further, a rotation phase position of the focus frame 5 is determined at a predetermined precision around the optical axis O through the boss portion 4 c of the first group frame 4 (see FIG. 7).

[0080] On the other hand, the first group lens 21, second group lens (front) 22, second group lens (rear) 24 and third group lens (front) 25 are precision fit to the inner peripheral face of the lens supporting portion, which is divided to three parts, and centered by the assembly jigs 32, 33. Additionally, they are brought into contact with the contact portions so that they are positioned in the direction of the optical axis O.

[0081] As described above, the respective lens groups are supported such that they are floated at an accurate position by the assembly jig 32.

[0082] Meanwhile, the outer peripheries of the first group frame 4 and third group frame 7 may be theoretically of a dimension allowing a loose fitting to the inner periphery of the jig 32. The reason is that the positioning accuracy of the guide shafts 8, 9 has been already determined.

[0083] The lens holding portions, which are divided to three sections each, of the first group frame 4, focus frame 5 and third group frame 7 are located along a circumference of each of the corresponding lens supporting inner peripheral faces, which are divided to three sections each, of the assembly jigs, 32, 33 and positioned with an appropriate gap for adjustment or bonding with respect to the outer peripheral face of each lens.

[0084] Further, with respect to a lens face of each lens in the direction of the optical axis O, there is an appropriate gap for adjustment of a position in the direction of the optical axis O and bonding between the pawl portion 4 g of the first group frame 4 or the lens holding end face 7 k of the third group frame 7 and a flange face (flange face 25 a of the third group lens 25) of each lens.

[0085] The guide shaft 11 fit and inserted into the focus frame 5 through the sleeve 10 supported with loose is maintained in an appropriate condition in the shaft hole even if there is disparity in the shaft hole between the first group frame 4 and third group frame 7 positioned by the guide shafts 8, 9.

[0086] If a leaf spring type lens holding mechanism or the like is incorporated to prevent deviation or slip-out of each lens mounted on the lens supporting portion although it is not indicated on each lens supporting portion of each of the assembly jigs 32, 33 shown in FIGS. 3, 4, assembly efficiency is further improved.

[0087] The sleeve and lens of the lens barrel 1 are bonded with adhesive agent (fixing agent) in a setting condition by the assembly jigs 32, 33.

[0088] First, bonding of the sleeve 10 is carried out by pouring adhesive agent through the adhesive agent pouring hole 5 b leading to the sleeve fitting hole 5 a provided in the outer peripheral portion of the focus frame 5.

[0089] Bonding of the first group lens 21 is carried out by pouring adhesive agent into a lens holding gap S1 formed by the lens holding portion 4 a, pawl portion 4 g and first group lens 21 through an opening hole 4 k, 4 l provided in the outer periphery of the first group frame 4 and the lens holding portion 4 a (see FIG. 5).

[0090] Instead of the pouring of the adhesive agent, it is permissible to coat the lens holding portion 4 a of the first group frame 4 with adhesive agent for the bonding.

[0091] Bonding of the second group lens (front) 22 is carried out by applying adhesive agent onto the lens holding portion 5 d of the focus frame 5 preliminarily and then filling a lens holding portion gap S2 formed by the lens holding portion 5 d, lens contact face 5 k and the outer diameter of the second group lens (front) 22 with adhesive agent.

[0092] Bonding of the second group lens (rear) 24 is carried out by pouring adhesive agent into a lens holding portion gap S3 formed by the lens holding portion 5 e, lens contact face 5 m and the outer diameter of the second group lens (rear) 24 through an opening hole 32 k provided in the outer periphery of the assembly jig 32.

[0093] Instead of the pouring of the adhesive agent, it is permissible to coat the lens holding portion 5 e of the focus frame 5 with adhesive agent for the bonding.

[0094] Bonding of the third group lens (front) 25 is carried out by applying adhesive agent onto the lens holding portion 7 d of the third group frame 7 preliminarily and filling a lens holding portion gap S4 formed by the lens holding portion 7 d, inside end face 7 k and the outer diameter of the third group lens(front) 25 with adhesive agent through an opening (not shown) provided in the outer periphery of the assembly jig 32.

[0095] Here, by bringing the third group lens (rear) 26 into contact with a rear side face of the third group lens (front) 25, adhesive agent is applied into a gap between the inner peripheral face 7 m formed the third group frame 7 and the outside diameter of the third group lens (rear) 26 for bonding.

[0096] When installing the third group lens (rear) 26, it is permissible to install the third group lens (rear) 26 while observing and adjusting alignment thereof entirely with the first group lens 21, second group lenses 22, 23, 24 and the third group lens (front) 25. Alternatively, it is permissible to mount the third group lens (rear) 26 while observing and adjustment alignment thereof with respect to assembly of the third group lens (front) 25 having no third group lens (rear) 26 and the third group frame 7.

[0097] Meanwhile, if the lens holding portion is filled with adhesive agent, there is a fear that the adhesive agent may flow out to the surface of the lens so that its optical performance may be damaged. Therefore, as shown in FIGS. 6A, 6B, 6C, the lens end face and/or lens holding end face is provided with a chamfered portion so as to prevent a flow out of adhesive agent.

[0098] That is, when the lens holding portion is protruded from a lens, for example, as shown in FIG. 6A, an end face 7 h of the lens holding portion 7 d of the third group lens 7 is protruded from the third group lens (front) 25. Thus, a chamfered portion 25 a is provided on an end face of the third group lens 25. By employing this configuration, adhesive agent 44 loaded in the gap S4 hardly flows out from the gap S4 to the surface of the lens.

[0099] Further, when the lens is protruded from the lens holding portion, for example, as shown in FIG. 6B, the second group lens (front) 22 is protruded from an end face of the lens holding portion 5 d of the focus frame 5. Thus, a chamfered portion 5 n is provided on an end face of the lens holding portion 5 d. By employing this configuration, adhesive agent 42 loaded in the gap S2 hardly flows out from the gap S2 to the surface of the lens.

[0100] Further, a state in which the lens holding portion and the lens are located on the same plane never exists in the lens barrel 1 of this embodiment. Because as shown in FIG. 6C, for example, the end face of the lens holding portion 13 d of the lens frame 13 and the lens 27 are located on the same plane if this state is attained, both the end face of the lens holding portion 13 d and the outer periphery of the lens 27 are provided with the chambered portions 13 a, 27 a. By employing this configuration, the adhesive agent 45 loaded in this gap S5 hardly flows out of the gap S5 to the surface of the lens.

[0101] If mounting and bonding of the guide shafts, lens and the like by the assembly jigs 32, 33 shown in FIG. 5 are finished, the jigs 32, 33 are removed from the lens barrel 1. At that time, the third group frame 7 is removed from the jig 32 and the first group frame 4 is removed from front with the guide shaft 11.

[0102] After the assembly jig 33 is also removed from front, the focus frame 5 and focus holding frame 6 are removed from the assembly jig 32 with the guide shafts 8, 9. FIG. 7 shows a longitudinal sectional view of the lens barrel 1 in a condition that the assembly jigs 32, 33 are removed to assemble those lens frames.

[0103] The reason why the removal of the lens barrel 1 is enabled even if the assembly jig 32 having the wall portion (wall face 32 g) is used, as described above, is due to the supporting structure of each guide shaft. That is, the guide shaft 11 is supported by the side of the first group frame 4 and the other frame members are supported slidably. Further, the guide shafts 8, 9 are supported by only the focus holding frame 6 disposed in the center and supported slidably by the other frame members.

[0104] After the above described installation is finished, the cam ring 2 is incorporated in the lens barrel 1 and then, the first group frame 4, the focus holding frame 6 and three cam followers 4 i, 6 i, 7 i of the third group frame 7 are fit into the three sets of the cam grooves 2 a, 2 b, 2 c in the cam ring 2.

[0105] Upon zoom driving, the cam ring 2 is driven from the collapsed position θC indicated by a rotation position with respect to the cam follower to the tele end position θT. As shown in FIG. 9, the cam follower introducing groove 2 d is provided at an introduction position θA, which is a rotation position outside the tele end position θT. Further, a joint groove 2 e for the cam follower to move is provided at a switch position θB, which is a rotation position outside the other collapsed position θC.

[0106] Then, in the respective cam grooves, the cam follower introducing groove 2 d and the joint groove 2 e are joined to each other and those cam grooves are disposed around the optical axis O such that they are formed to extend side by side in a length direction thereof and the cam groove 2 a, cam groove 2 b and cam groove 2 c are arranged in this order from the object side.

[0107] The cam follower introducing groove 2 d is a groove in the direction of the optical axis O provided for joining the tele side end portions of the cam groove 2 b and cam groove 2 c and its insertion mouth is open to a rear side. The joint groove 2 e is a groove in the direction of the optical axis O for joining the collapsed side end portions of the cam groove 2 a and the cam groove 2 b.

[0108] When fitting the cam follower into the above described cam grooves, the cam follower introducing groove 2 d and the joint groove 2 e are used.

[0109] First, the cam follower 4 i of the first group frame 4 shown in FIG. 7 is positioned at a cam ring insertable position and then, the cam ring 2 is rotated up to the introduction position θA so as to be inserted into the lens barrel 1. Then, the cam follower 4 i enters from the opening portion 2 g of the cam ring 2 into the cam follower introducing groove 2 d.

[0110] If the cam follower 4 i reaches the end position of the cam groove 2 b, the cam ring 2 is rotated clockwise up to the switch position θB. By that rotation, the cam follower 4 i passes the cam groove 2 b and reaches the joint groove 2 e. Then, the cam ring 2 is pushed relatively to the rear side of the lens barrel so that the cam follower 4 i is fed to the end position of the cam groove 2 a on the front side. Next, the cam ring 2 is rotated counterclockwise so as to be returned to the introduction position θA.

[0111] Next, the cam followers 6 i, 7 i of the focus holding frames 6 and the third group frame 7 are set in the cam ring insertable position. Next, if the cam ring 2 is pushed relatively to the rear side of the lens barrel, the cam followers 6 i, 7 i enter from the opening portion 2 g of the cam ring 2 into the cam follower introducing groove 2 d.

[0112] Then, if the cam follower 6 i reaches the position of the cam groove 2 b and the cam follower 7 i reaches the position of the cam groove 2 c, the cam ring 2 is rotated clockwise. The cam follower 6 i enters the cam groove 2 b and the cam follower 7 i enters the cam groove 2 c. Meanwhile the cam follower 4 i is kept in the cam groove 2 a and then, entering the cam groove of each cam follower into the cam ring 2 is finished.

[0113] After that, the guide protrusion 7 f of the third group frame 7 is fit into an advancement guide groove 3 a provided in the front key 3 and then, the third group frame 7 is kept capable of being advanced or retracted while its rotation is restricted by the front key 3. Consequently, the assembly of the lens barrel 1 of this embodiment is finished.

[0114] When the lens barrel 1 is in the collapsed condition, the cam ring 2 is rotated to the collapsed position θC shown in FIG. 9 and further, introduced to the collapsed position in the direction of the optical axis O.

[0115] Then, the cam ring 2 is introduced up to a photographing possible position along the optical axis O and the collapsed region A1 (see FIG. 9) is rotated counterclockwise to the wide end position θW through the zoom driving portion. By this rotation, the respective cam followers 4 i, 6 i, 7 i are advanced or retracted relatively by the cam grooves 2 a, 2 b, 2 c. The first group frame 4 and the focus holding frame 6 and the third group frame 7 are moved to the zoom wide end position enabling photographing along the optical axis O.

[0116] If the cam ring 2 is zoom driven throughout the zoom region A2 (see FIG. 9) up to the tele end position θT by the aforementioned zoom driving portion, the respective cam followers 4 i, 6 i, 7 i are advanced or retracted relatively by the cam grooves 2 a, 2 b, 2 c. Consequently, the first group frame 4, the focus holding frame 6 and third group frame 7 are moved from the zoom wide end position to the zoom tele end position along the optical axis O.

[0117] The focusing drive of the lens barrel 1 is carried out by advancing or retracting the focus frame 5 relative to the zoom-driven focus holding frame 6 along the optical axis O by means of a focus driving portion (not shown).

[0118] In the lens barrel 1 of an embodiment described above, the first group frame 4, the focus frame 5, the focus holding frame 6, and third group frame are supported by the guide shafts 8, 9 and 11 such that they are capable of being advanced or retracted. The guide shafts 8, 9 are fixed at the focus holding frame 6 located substantially in the center and both ends of the guide shafts 8, 9 are slidable with respect to the first group frame 4 and third group frame. In other words, the first group frame and third group frame are capable of sliding in the direction of the optical axis at both ends of the guide shafts 8, 9.

[0119] Therefore, as compared to a conventional type in which the frame members are supported by the lens barrel such that both ends of the guide shafts are fixed to the frame members, a restriction of moving space for the first group frame and third group frame is decreased, thereby contributing to reduction of the size. Further, as compared to cantilever type in which an end of the guide shaft is fixed and supported by conventional the lens barrel, the shaft span is shortened so that distortion is decreased. Consequently, more accurate advancement/retraction drive of the frame member can be realized. Further, the diameter of the guide shaft can be decreased thereby also contributing to reduction of the size of the lens barrel.

[0120] Further, the guide shaft 11 supports the focus frame 5, whose rotation around the guide shaft 11 is restricted by the boss portion 4 c of the first group frame 4, slidably through the sleeve 10. An end of the guide shaft 11 is supported by the shaft hole 4 f of the first group frame 4 as shown in FIG. 8 and the other end is supported freely slidably by the shaft hole 7 c of the third group frame 7. Further, because the fitting lengths of the shaft holes 4 f, 7 c are short and an inclination of the guide shaft 11 has a freedom so that it is capable of being unparallel to the guide shafts 8, 9, a disparity and error of dimension of the first group frame 4 or third group frame 7 can be absorbed not to obstruct a motion of the first group frame 4 and third group frame 7.

[0121] Further, if the diameter of the guide shaft 11 is small, a high load torque is applied between the focus frame 5 and the focus holding frame 6 when the focusing is driven. At this time, if the guide shaft 11 is about to be twisted largely, the focus frame 5 is prevented from being deviated largely, because the fitting outer circumferential portion 5 f of the focus frame and the fitting outer circumferential portion 6 e of the focus holding frame are fit to each other slidably.

[0122] According to the present invention, even if the dimensional accuracies of the respective frame members are decreased to some extent within an allowable range, a high accuracy as the lens barrel is maintained, thereby contributing to reduction of production cost of the parts. At the same time, because the respective members can be installed to the guide members in a relatively easily movable condition, the assembly thereof is facilitated. Further, because only three shafts are employed as the guide members for supporting the four frame members, an occupied space is small, thereby making it possible to produce a small lens barrel. 

What is claimed is:
 1. A lens barrel comprising: a first frame; a second frame; a third frame; and a first supporting member fixed to said second frame with both ends thereof exposed, wherein said both ends thereof support said first and third frames.
 2. A lens barrel as claimed in claim 1 wherein said first frame is supported movably by said first supporting member.
 3. A lens barrel as claimed in claim 1 wherein said second frame is supported by said first supporting member and the second frame is movable integrally with said first supporting member.
 4. A lens barrel as claimed in claim 1 wherein said third frame is supported movably by said first supporting member.
 5. A lens barrel as claimed in claim 1 wherein at least one of said first frame, said second frame and said third frame is movable in the direction of the optical axis.
 6. A lens barrel as claimed in claim 1 wherein said first supporting member is a bar-like member.
 7. A lens barrel as claimed in claim 1 further comprising: a second supporting member supported by said first frame and said third frame; and a fourth frame supported by said second supporting member, said fourth frame being movable relatively between said first frame and said second frame.
 8. A lens barrel as claimed in claim 7 wherein said fourth frame has a sleeve member and said second supporting member is fit to said sleeve member so as to support said fourth frame.
 9. A lens barrel as claimed in claim 8 wherein said sleeve member is capable of being fit to a hole with loose fitting provided in said second frame in non-contact condition.
 10. A lens barrel as claimed in claim 7 wherein said second supporting member is supported tiltably relative to said first frame and supported slidably by said third frame.
 11. A lens barrel as claimed in claim 7 wherein an end of said second supporting member is precision fit to said first frame and the other end of said second supporting member is precision fit to said third frame while fitting lengths thereof are short.
 12. A lens barrel as claimed in claim 8 wherein said sleeve member is fit to a hole with loose fitting provided in said fourth frame and bonded.
 13. A lens barrel comprising: frame members; and a bar-like guide member fixed to one of the frame members between both end portions the bar-like member, said both ends supporting other frame members slidably relative to one of the frame members.
 14. A lens barrel as claimed in claim 13 wherein the frame member on which said guide member is fixed is a movable frame.
 15. A lens barrel comprising: a first frame member movable within the lens barrel; a second frame member movable within the lens barrel; a third frame member movable within the lens barrel; and a first guide member composed of a bar-like member, having two end face portions wherein a central portion of the bar-like member supports said second frame member while one end face portion thereof guides said first frame member and the other end face portion guides the third frame member.
 16. A lens barrel as claimed in claim 15 further comprising: a second guide member supported by said first frame member and said third frame member; and a fourth frame member guided by said second guide member so that said fourth frame member is movable relatively between said first frame member and said second frame member.
 17. A lens barrel as claimed in claim 16 wherein said fourth frame member has a sleeve member and said second guide member is fit to said sleeve member so as to guide said fourth frame member.
 18. A lens barrel as claimed in claim 17 wherein said sleeve member is capable of being fit to a hole with loose fitting provided in said second frame member in non-contact condition.
 19. A lens barrel as claimed in claim 16 wherein said second guide member is supported tiltably by said first frame member and supported slidably by said third frame member.
 20. A lens barrel as claimed in claim 16 wherein an end of said second guide member is precision fit to said first frame member and the other end of said second guide member is precision fit to said third frame member while the fitting lengths are short.
 21. A lens barrel as claimed in claim 17 wherein said sleeve member is fit to and bonded to a hole with loose fitting provided in said fourth frame member. 